What is Confusing: Definition and 407 Discussions

In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion" is often used interchangeably with delirium in the International Statistical Classification of Diseases and Related Health Problems and the Medical Subject Headings publications to describe the pathology. These refer to the loss of orientation, or the ability to place oneself correctly in the world by time, location and personal identity. Mental confusion is sometimes accompanied by disordered consciousness (the loss of linear thinking) and memory loss (the inability to correctly recall previous events or learn new material). The term is from Latin: confusĭo, -ōnis, from confundere: "to pour together", "to mingle together", "to confuse".

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  1. L

    Mathematica Very confusing problem in Mathematica

    Hi everybody, Last time I was here I was asking about finding roots but many things have progressed. Anyway I have another problem now. I have a linear system of equations which I'd like to solve: A.X==B And I tried two things: get the inverse of A and multiply it with B and also use...
  2. Z

    Thermodynamics problem really confusing

    A irreversible heat engine operating between heat reservoirs at 600 K and 300 K has half the efficiency of a Carnot engine. Calculate the entropy change of the working fluid in the engine which is the system, the surroundings, and the universe per cycle of the engine if 1000 J are extracted from...
  3. W

    Proving Closure of Set T: f(x)=g(x) on Closed Domain [a,b] in R

    Suppose f:[a,b]--> R and g:[a,b]-->R. Let T={x:f(x)=g(x)} Prove that T is closed. I know that a closed set is one which contains all of its accumulation points. I know that f and g must be uniformly continuous since they have compact domains, that is, closed and bounded domains. Now T is the...
  4. K

    Tension, very simple , but confusing

    We have a car stuck in the mud. To pull it out we have tied a rope on it and began pulling in one direction horizontally. Another method was proposed that one end of the rope was tied to the car and the other was tied to the nearby tree and then the same amount of force was applied perpendicular...
  5. N

    Find Values of a, b, c, and d for f(f(x)) = x | Confusing Problem Solution

    Homework Statement For which numbers a, b, c, and d will the function f(x) &= \frac{ax+b}{cx+d} satisfy f(f(x)) = x for all x (for which this equation makes sense. Homework Equations The Attempt at a Solution I'm not sure if the answer will consist of specific values, or just a general...
  6. F

    Solving Confusing Exercises: Understanding Water Displacement and Density

    Hi First of all I'd like to say that I don't want to put this under "Homework help", because its not really homework. But it is something I can't wrap my mind around. There are 2 tasks: 1) There's 200 cm3 water in a glass. How high does the water level rise / how much does the cubage...
  7. X

    Intersections and Unions of powersets confusing

    Homework Statement let A and B be finite sets Let P(A) denote the Power Set of A (set of all subsets of A)Homework Equations Prove or disprove: a) P(A inter B) = P(A) inter P(B) b) P(A U B) = P(B) U P(B) The Attempt at a Solution So I tried drawing Venn diagrams and came to the conclusion...
  8. M

    Demystifying Quantum Numbers: Understanding the Role of n, l, and ml

    I am still totally confused about the principle quantum number even though i got passed the unit with a A+ on the exam. does the principal quantum number, n, have anything to do with the period? Does the "n" value, which leads to the "l" and "ml" actually indicate all the possible orbitals for a...
  9. B

    Confusing projectile motion problem?

    Homework Statement You are designing software for an anti-aircraft system. Your guns have a maximum horizontal range R, and can be fired at any angle (call it "A") above the horizontal. Enemy aircraft are spotted at time t=0, flying at altitude H, distance D, horizontal velocity V toward a...
  10. K

    Confusing about linearity and nonlinearity

    Hi there, in the course of linear algebra, we talk about many on matrix and related properities. I wonder if any equations written in terms of matrices are linear? Could nonlinear equations also written in matrices? Thanks
  11. K

    Can a Quantum Mechanic Fix Your Physics Problems?

    So there is this guy named David Franklin Farkas of Amherst. His website is http://househealing.com . He "recently started a business psychically checking buildings for damage and repairing any 'holes' he finds in the energetic structure. It may sound like something from a sci-fi story, but...
  12. R

    Confusing Elastic and Inelastic Collisions :S

    Can someone please 'stupify' the definitions of an elastic and inelastic collision? Do objects bouncing off of each other undergo elastic collisions, while objects which stick together undergo completely inelastic collisions? This concept is very confusing to me :S thank you!
  13. C

    Confusing Limit Problem: Solving lim[x→-2¯(from the left)] x+2/sqrt(x^2-4)

    Homework Statement lim[x→-2¯(from the left)] x+2/sqrt(x^2-4)Homework Equations The Attempt at a Solution When I attempted this question I felt that the solution was that this is undefined and when i put it into my ti-89 it said that too. My friend argues that it's...
  14. N

    Dispersion of light in a prism confusing

    I understand that as the frequency of an electromagnetic wave increases, its refractive index decreases in a material. According to this, red light would have a higher refractive index than blue light (is my mistake here? why?). Since sinI/sinR = n (where I is the angle of incidence, R is the...
  15. S

    Understanding the Confusion Behind Comb(x) and III(x) Definitions in Mathematics

    comb(x) (or III(x), or Shah(x), whatever you want to call it) is DEFINED as the infinite sum of delta functions. III(x)=\sum_{n=-\infty}^{\infty}\delta(x-nT) for some period T. We know that \delta(x-a) is the shifted delta function where a is some constant. We also know that \delta...
  16. L

    Limits of 0<x<1: Exploring Confusing nx Term

    Homework Statement This should be easy but I can't find why. Why is the following true for 0<x<1, \lim_{n \rightarrow \infty}nx(1-x^2)^n = 0 Homework Equations The Attempt at a Solution I understand why (1-x^2)^n goes to zero, but the nx part is not bounded and seems to...
  17. J

    Dirac delta function - its confusing

    Hi I have been trying to learn dirac delta function. but its kind of confusing. I come across 2 contrasting definitions for it. The first one states that the function delta(x-xo) is infinite at x=x0 while the other states that delta(x-x0) tends to infinite as x tends to x0. Now both of them...
  18. M

    Kinematics of a Watch's Second Hand: Calculating Speed and Velocity

    Homework Statement A watch has a second hand 2.0cm long. a) compute the speed of the tip of the second hand. b) What is the velocity of the tip of the second hand at 0.0s and 15s Homework Equations No Idea... The Attempt at a Solution I drew a clock...but I don't even know...
  19. A

    Calculating Force Exerted on 17-kg Box from 90-N Force Acting on 11-kg Box

    Homework Statement Two boxes are sitting side on a frictionless surface. The box on the left has a mass of 11kg and the box on the right has a mass of 17kg. If a 90-N force pushes on the 11-kg box from the left, what is the force exerted on the 17-kg by the 11-kg box? A) 55 N B) 43 N C)...
  20. E

    Understanding (0,1)-Tensor in Relativity

    I have just starting learning relativity and I have still a problem with the definition and notation of tensors. So a (r,s)-tensor takes r vectors, s one-forms and gives a scalar. Then I understand that a (1,0)-tensor takes 1 vector (e.g. from V) and gives a scalar which is exactly the...
  21. M

    Resistance of a loop of wire: confusing

    Dear physics forums I am an A-level physics teacher and I have built, admittedly, a VERY simple circuit. The problem is that I cannot explain its behaviour. It involves a metre long wire, twisted at the ends to form a loop, and incorporated into a circuit as shown below: (or attached)...
  22. P

    Mechanical Energy question (Skier going down a slope confusing )

    Mechanical Energy question (Skier going down a slope...confusing!) First of all, I apologize ahead of time if my question seems to be really simple, but I have been working on it for at least two hours and still no progress (which is why this post made so late lol). My class has been working on...
  23. M

    Short yet confusing log equation

    Homework Statement Solve the equation log x4 - log x3 = log 3x - log 2x I know the laws of logs and I cleared all the other log questions in seconds but I can't figure this one out Homework Equations I know that log x4 - log x3 is the same as log x4/x3 but what I was wondering is if...
  24. K

    Confusing on permeability and relative permeability

    In some textbook of fundamental electromagnetism, the relation between magnetic field \vec{B} and so called magnetizing field \vec{H} is \vec{B} = \mu_0\vec{H} But later on, they introduce a so called relative permeability \mu_r = \frac{\mu}{\mu_0} I might be wrong but my...
  25. D

    Electromagnetic Waves: A Confusing Abstraction

    I am having some trouble understanding the concept of electromagnetic waves, I suppose because I expect them to be analogous to physical waves you can see or touch (such as on a string). Yes, I know one can actually see them at visible wavelengths, but that doesn't help because I don't...
  26. V

    Understanding Force Statements: Solving a Confusing Homework Problem

    Homework Statement A person is pushing an object of mass m along the ground with force F. The coefficient of kinetic friction between the object and the ground is (mu)k. The object is accelerating, but then the person stops pushing and the object slides to a halt. The person then starts...
  27. A

    Calculating Angular Momentum: Uniform Rod and Point Mass Collision

    Homework Statement A uniform rod (M 4.4 kg, L 0.827 m) starts at rest on a frictionless table. A point mass = 0.808 kg hits the rod at a right angle at speed 6.39 m/s. The block strikes the rod at a distance of 0.12 m below the center of mass, and stops. Assume the block does not stick to the...
  28. A

    Torques exerted by Gravity (CONFUSING)

    Homework Statement A door with symmetry and of m 43.1 kg is 4.76 m high and 2.68 wide. The hinges are placed all the way on top and all the way on the bottom of the door. Find the absolute value of the horizontal force supplied by the bottom hinge.Homework Equations Sum of torques = 0 Torque =...
  29. S

    Converting Celsius to Kelvin Easy but slightly confusing

    Homework Statement I'm doing calorimetry, and I have 34.73C and 63C. I need to subtract 63 from 34.73, and get the answer in Kelvin. Homework Equations The Attempt at a Solution I know you add 273 to Celsius values to get Kelvin, but I am not sure which of these methods is correct: 1...
  30. A

    Confusing ROTATIONAL RIGID BODY QUESTION problem conceptualizing

    Homework Statement A piece of cloth with irrelavent mass is wrapped around a 67.5 kg cylinder of radius 0.167 m. Joe holds the free end of the cloth. The cylinder is released from rest, and Joe pulls the tape upward at a speed that just prevents the center of mass of the cylinder from falling...
  31. A

    Rotational KINEMATICS (confusing)

    Homework Statement a) A 1.79 kg toy train accelerates constantly from 0.82 m/s to 3.43 m/s in 0.479 revolutions while traveling around a circular track of r 16.7 cm. Find: - α, magnitude of the angular acceleration.Homework Equations The Attempt at a Solution I first tried getting...
  32. H

    A confusing trigonometric question

    A confusing trigonometric question! Hi guys, I had a question. I was given the following equality. There was no problem statement that came with it (i.e. it did not say solve the equation or prove the identity, or anything of this nature) sec x + csc x / tan x + cot x = sin x + cos x The...
  33. A

    Conservation of momentum (extremely easy but confusing)

    Homework Statement If the mass of an object increases, its momentum A. always increases B. always decreases C. sometimes increases, sometimes decreases D. sometimes decreases, never increases E. sometimes increases, never decreases Homework Equations MV=momentum The Attempt at...
  34. A

    Circular Motion: 2-step System (very confusing)

    1. http://paer.rutgers.edu/PT3/experiment.php?topicid=5&exptid=177 The three black stoppers that are whirling in a circle have a combined mass of 58.7g. The length of man's arm from elbow to wrist is about 30 cm. 2. Find the mass of the other object that is tied at the bottom. 3. I solved for...
  35. F

    Limit of ln(n)/ln(n+1) as n->+infinity, very confusing

    Limit of ln(n)/ln(n+1) as n-->+infinity, very confusing can someone help me find the lim as n approaches infinity of ln(n)/ln(n+1) I used L'HOP so it became (1/n)/(1/n+1) -- as this approaches infinity, it's 0/0, and this confuses me. What am I doing wrong?
  36. G

    [Q]Some confusing about Dirac Delta Function

    Hi. Recently day, I tried to solve quantum mechanics problem in liboff fourth version to prepare graduate school. But what make me be confused a lot is Dirac Delta Function. One of my confusing on Dirac Delta is what i wrote below. -One of the formula describing Dira Delta...
  37. wolram

    The Confusing World of Fashion: A Bewildering Experience

    Do you find these creatures attractive? i think they have been made into a parody of what the chick/arty people think is cool. And the way they walk what the, who thought that up? And the clothes? a lot of them make the wearer look a real plonker. Yes i watched a fashion show on tv and...
  38. A

    Calculating Delta h for a Projectile Fired at 50 Degrees without Air Resistance

    Homework Statement A cannon fires a 0.626 kg shell with initial velocity vi = 9.6 m/s in the direction θ = 50◦ above the horizontal. The shell’s trajectory curves downward be- cause of gravity, so at the time t = 0.392 s the shell is below the straight line by some verti- cal distance...
  39. H

    Calculation of Salt Content in Stirred Tank with Brine Inflow and Outflow

    Homework Statement A tank contains 1000 gal of water in which 200 lb of salt is dissolved. 50 gal of brine, each gallon containing (1 + cos t) lb of dissolved salt, runs into the tank per minute. The mixture, kept uniform by stirring, runs out the same rate. Find the amount of salt in the...
  40. P

    Calculating Lift Force and Air Resistance in a Moving Helicopter

    A helicopter is moving horizontally to the right at a constant velocity. The weight of the helicopter is W = 57600 N. The lift force L generated by the rotating blade makes an angle of 21.0° with respect to the vertical. (a) What is the magnitude of the lift force in N? (b) Determine the...
  41. F

    Understanding Complete Function Expansion: A Confusing Concept

    i thought i understand it but i guess i don't... you can expand a function in cosine f.s., sine f.s. and complete f.s. on some [0..L]. i thought that the coefficients a_n and b_n for complete expansion would come from sines and cosines respectively, but i guess that wouldn't make sense...
  42. H

    Solving for Velocity and Acceleration Error: A Confusing Task

    Hi everybody! This might seem like a terribly easy question, but I can't seem to figure it out for the life of me. I've been given a set of values for time and velocity: t (s) v (m/s) 0 0 3 7 7 16 12 33 18 48 23 53 27 67...
  43. M

    Simplifying a Confusing Force Problem: Understanding Acceleration and Magnitude

    Here is a picture of the problem. The question is: A force F0 causes an acceleration of 17 m/s2 when it acts on an object of mass m sliding on a frictionless surface. Find the magnitude of the acceleration of the same object in the circumstances shown in each figure below. Figure (a)...
  44. S

    Conditional Probability (confusing)

    Dear all, P (A |B) + P (A c|B) = 1 [A c] denotes complement of set A and of course P (B)>0 Is the above statement true? How about the following two: P (A |B) + P (A |B c) = 1 P (C ∪ D|B) = P (C |B) + P (D|B) − P (C ∩ D|B)
  45. F

    Confusing projectile motion problem - need guidance

    Confusing projectile motion problem -- need guidance Here is the picture of the diagram. The Question: A woman throws a ball at a vertical wall d = 3.6 m away. The ball is h = 1.8 m above ground when it leaves the woman's hand with an initial velocity of 16 m/s at 45°. When the ball hits the...
  46. F

    Understanding Exponent Rules: The Confusion of (-8)^(2/6)

    hello.i have a weird problem. (-8) ^ (2/6) = ? my first instinct was to simplify the exponent, which yields (-8) ^ (1/3) = -2. this is the answer the calculator gives as well. but someone pointed out if you don't simplify that exponent, you have the sixth root of (-8^2), which would...
  47. C

    Calculate Total Fall Time with Kinematic Equations | FreeFall Question

    Homework Statement A rock is thrown horizontally from a cliff with a speed of 15 m/s. It falls half of the heigh of the cliff in the last three seconds of its fall. What is the total fall time? Homework Equations The Kinematic Equations The Attempt at a Solution Well here's what I...
  48. 8

    Liveweaver's Paper On Expanding Confusion Is Confusing

    arXiv:astro-ph/0310808v2 paper by Lineweaver dated 13 Nov 2003 entitled "Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the universe" has a sentence in the second paragraph on page 4 that I find confusing. The sentence is: "However, since...
  49. F

    Demystifying Torque: A Visual Guide

    to be able to understand my point of view please check this picture which I attched>> the question is in the picture please check it thanks
  50. F

    Confusing chain differentiation rule

    If I have a function f from RxR to R, and a function g from RxR to RxR. What are the partial derivatives of the composition f(g)? I end up multiplying the derivative of f with g, but g is a vector? The partial derivative should have its image in R.
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